Study On HDPE/CB PTC Conductive Composite And Appliance

A new kind of PTC conductive composite and its appliance, self-regulating heating cables , which has been used by Beijing Xiechang Cable Factory, Qiangli Plastics Factory and gain 100000yuan,was studied and developed in this paper. By means of DSC, TEM, WAXS, the percolation transition, PTC effect, stability, processability of HDPE/CB composites were studied systematically.1 The electrical conductive PTC composites of various crystallity were studied and the mechanism of PTC effect was discussed. It is supposed that the PTC effect is relation to the crystalline behavior of matrix.2 The relations between the data of thermal behavior and characteristic temperature of self-regulating heating cables were first studied systematically. It is showed that heat deformation temperature is same as working temperature of cable; Vicat softening point is close to the switch temperature. Based on the observations, HDPE was choose to be the matrix of self-regulating heating cable.3 The percolation transition and PTC effect of various types CB filled HDPE composites were studied. The influences of property and fraction of CB on the PTC behavior and crystallity were studied. It is first founded that CB can induce the crystallity of HDPE. It is supposed that the PTC effect is relation to the disperse of CB particles.4 The PTC effect and stability of g-HDPE/CB were studied. It showed that PTC behavior was similar with HDPE/CB, but the crystallity of g-HDPE was lower than HDPE/CB. The PTC intensive, resistivity, heating temperature and power of the cable made from g-HDPE were changed lower than 15% for 7200 hours. The results showed that g-HDPE could improve the heating stability.5 The PTC effect and stability of HDPE/PVDF/CB were studied. It showed that: percolation threshold reduced from 18% to 12%, with the fraction of PVDF improve and PVDF could improve the heating stability and reduce NTC characteristic of composites. It was first reported that the heating temperature of the cable made from HDPE/PVDF/CB were 85 C ~95 C for 7200 hours in our country.6 The effect of radiation cross-linking on stability of HDPE/CB was studied systematically. The result showed that with increasing of irradiation dose, the PTC reproducibility was improved and the NTC characteristic was reduced. The radiation cross-linking is the best way to improve the stability and reduce NTC characteristic. The cable irradiated with 380kGy display excellent thermo electrical character and can be used.7 The influence of extrusion processing factors of HDPE/CB composite was systematically studied. The results showed that the performances of PTC self-regulating heating cable depend on the die temperature, screw speed and cooling methods. So it is important to control the processing conditions.8 The characteristic of the self-regulating heating cable we producedare similar with the foreign cable, but the price of our cable is the 1/3 of them. So it has a bright outlook. Now, 5000metres self-regulating heating cable has been produced for antifreezing fire application by Beijing Xiechang Cable factory.